Question

Anoxygenic photosynthesis is a characteristic feature of
(A) Spirogyra.
(B) Chlamydomonas.
(C) Ulva.
(D) Rhodospirillum.

Answer 1

Hint: Anoxygenic photosynthesis is a characteristic feature of that bacteria that is gram-negative, motile, and spiral in shape. It is also used as a nitrogen fixation bacteria. They are generally found in marine environments.

Complete step by step answer:
Anoxygenic photosynthesis is a characteristic feature of Rhodospirillum. Some of its species are Rhodospirillum centenum, R. photometricum, and R. rubrum.
Rhodospirillum rubrum is a type of purple nonsulfur bacteria which can grow aerobically or anaerobically. It's the flexibility to measure through respiration, fermentation, photosynthesis, or photoautotrophic growth.
In Anoxygenic photosynthesis, light energy is utilized and is converted to ATP without the production of oxygen. In this, water is not used as a source of energy. Hydrogen is obtained from other inorganic and organic compounds like ${ H }_{ 2 }{ S }$. They can be grown under many various kinds of conditions including aerobic or anaerobic environments. Anaerobically, the bacterium uses fermentation or photosynthesis so as to supply energy also as photoautotrophic growth (DOE). The nitrogen fixation system of R. rubrum uses a MoFe and a Fe-only nitrogenase. Rhodospirillum bacteria can generally be found in marine environments or in some sorts of mud and soil where light is accessible for photosynthesis. The reaction of anoxygenic photosynthesis is-
${ 6 }{ C }{ O }_{ 2 }+12{ H }_{ 2 }{ S }+{ Light }\rightarrow { C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }+{ 12 }{ S }+{ 6 }{ H }_{ 2 }{ O }$

So, the correct answer is ‘Rhodospirillum'.

Note: In oxygenic photosynthesis, the process depends on chlorophyll i.e chlorophyll helps in absorbing light, and then the transfer of electrons takes place but in anoxygenic photosynthesis, the organism depends on bacteriochlorophylls. Bacteriochlorophyll differs from chlorophyll 'a' in having Bacteriochlorophyll differs from chlorophyll 'a' in having One pyrrole nucleus with two hydrogen.